Redundantable robot assembly for workpiece transfer

ABSTRACT

A redundantable robotic mechanism is disclosed for improving reliability of tranport equipment. The redundantable robot assembly typically comprises independent robots with separate controls, motors, linkage arms, or power, thus providing the capability of operation even if parts of the assembly are not operational or when parts of the assembly are removed for repair. The redundantable robot assembly can be also designed to allow in-situ servicing, e.g. servicing one robot when the other is running. The disclosed redundantable robot assembly provides virtual uninterrupted process flow, and thus greatly increases the yield for the manufacturing facility.

This application claims priority from U.S. provisional patentapplication Ser. No. 60/849,997, filed on Oct. 6, 2006, entitled“Redundantable robot assembly for workpiece transfer”; which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to apparatuses and methods to transferobjects, and more particularly to multiple independent robot assemblyfor reliably moving multiple workpieces, such as semiconductor wafers orreticles.

BACKGROUND

Robot assemblies are an important component in automation, especially inmanufacturing facilities and manufacturing equipments. For example, inthe semiconductor industry, robot arms are used to handle semiconductorwafers, flat panel display, LCD, reticles, masks, or carrier boxes.

In the semiconductor fabrication facility, robot can be used totransport workpieces, typically stored in carrier boxes, from onelocation to another location, from one equipment to another equipment.In a process system, a robot is typically used to remove the workpiecesfrom the carrier boxes, and then loaded into a loadlock. Another robotcan be used to move the workpiece from the loadlock into a processingchamber, and from one processing chamber to another processing chamber.Thus within a processing system, there might be a plurality of robots,each one is designed for a particular task. The processing system couldbe a deposition system, an etch system, a lithography system, ametrology system, an inspection system, an implantation system, atreatment system, or any workpiece processing system.

Another type of equipment is supplemental equipment such as a stocker,designed for storing the workpieces until needed, or a sorter, designedfor sorting the workpieces into certain desirable order. In a typicalbare stocker system, a robot is typically used to remove the workpiecesfrom the carrier boxes, and then loaded into a loadlock. Another robotcan be used to move the workpiece from the loadlock into a storagechamber, where the workpieces are stored without the original carrierboxes. For box stocker system, the workpieces are stored together withthe carrier boxes, without the need for removing them out of the carrierboxes.

Robot handling can be considered overhead operation, since the purposeof robot handling is to transport the workpieces between locations. Thusto improve the efficiency of the fabrication facility and to improve thethroughput of the equipment, faster movement of robots, and multiplerobot assemblies can be used. Thus some equipment provides a robotassembly with multiple carrier arms, to allow the transfer of multipleworkpieces. The multiple carrier arms are typically not independent, andthus maximum efficiency cannot be realized. Another robot configurationincludes multiple independent robot arms which can move independently,and thus can essentially double the throughput with one robot. Stillanother robot configuration includes two separate robots to transportthe wafers for an ion implantation system.

Robot is an integral part of many equipments, which provides the mostmovement within the equipment, thus is prone for failure, especiallywith the drive for faster robots. The equipment can be down and thefacility stops with a simple failure in the robot assembly.

SUMMARY

The present invention discloses apparatuses and methods for improvingreliability of equipment using redundantable robotic mechanism. In oneembodiment, the present invention discloses a redundantable robotassembly for certain critical operations of the equipment. In oneaspect, the components of the redundantable robot assembly areredundant, i.e. the assembly still operates even with the failure ofmany components. In another aspect, the redundant components of theassembly contribute to the normal operations.

In one embodiment, the redundantable robot assembly is designed foroptimum usage of the whole assembly during operating conditions. Theredundant parts of the redundantable robot assembly are designed tooperate under normal operating conditions. Thus when parts fail, theredundantable robot assembly will still operate, but under sub-optimumconditions. For example, a two-robot redundantable robot assemblyaccording to the present invention can process 100 wafers per hour undernormal operating conditions. If a robot fails, the assembly stilloperates, but with only one robot, and therefore the throughput isreduced to 50 wafers per hour. In other aspect, the redundantable robotassembly is designed for partially redundant components where theassembly is operating at sub-capacity.

In one embodiment, the redundantable robot assembly comprisesindependent robots with separate controls, motors, linkage arms, orpower. In other aspect, the redundantable robot assembly can comprisemultiple independent, separate robots which can operate even if parts ofthe assembly are not operational or when parts of the assembly areremoved for repair.

In other embodiment, the redundantable robot assembly is designed toallow servicing parts of the assembly when the other parts areoperating. In one aspect, the inoperative parts can be serviced,repaired or replaced at the original location. In other aspect, theredundantable robot assembly comprises removal mechanism to move theinoperative parts out of the way for repair or replacement. The movementof inoperative parts can be automatically or manually. In either case,the operation of the remaining robot assembly should be minimallyaffected during the servicing operation.

In other embodiment, the present invention provides a seamless operationwhen an inoperative part of the assembly is detected. The robotoperations bypass the inoperative part, and switch the transportmovement to the operative parts. In one aspect, the redundantable robotassembly provides movements of the remaining operative parts around theinoperative parts, as not to let the inoperative parts blocking theoverall operations of the assembly. In other aspect, when theinoperative parts are repaired and ready to resume operation, theassembly can seamlessly transfer the operations to the newly repairedparts. The assembly can also wait for an appropriate moment, such asafter a workpiece completion, or a lot completion before incorporatingthe repaired part into the normal operations.

In another embodiment, the present invention discloses a redundantablerobot assembly having two (or more) independent robots, designed andpositioned to provide essentially the same transport operations to theworkpieces. In certain aspects, design trade off can be consideredbetween design complexity and blind spots for robot reach. The robotscan be position side by side, top by bottom, offset, or any otherconfigurations. The robots can have articulate linkage arms, and eachrobot can also have multiple dependent or independent arms. The robotscan provide radial, rotational and vertical motions, or can providesvirtually any movements, such as a 6-axis robots.

In another embodiment, the present invention discloses a redundantablerobot assembly having a plurality of sensors to detect the operativeparts and the inoperative parts of the assembly. When an inoperativepart is detected, the assembly switches operations, allowing seamlessoperation of the equipment with minimum down time. When the inoperativepart is operative again, the assembly automatically switches backoperations, including calibration before operation.

In other embodiment, the present invention discloses softwareinstructions to operate a redundantable robot assembly. In one aspect,the robots in the redundantable robot assembly can operateindependently. In other aspect, the operating instructions of theredundantable robot assembly provide instructions to operate parts ofthe robot assembly to accommodate the other inoperative parts, oroperating instructions to calibrate the parts after being serviced, e.g.repaired, or replaced. The operator can be notified of the failure ofparts of the assembly. The operating instructions can also provide anejection operation to move the inoperative parts of the redundantablerobot assembly out of the operation range for ease of repair. Theoperating instructions can also provide the merging of the repairedparts back into operation with minimum disruption of the robot assembly.

In one embodiment, the present invention is used in atmosphericenvironment to facilitate the in-situ repair of inoperative parts. Inanother embodiment, the present invention can be used in sub-atmosphericenvironment. The sub-atmospheric operation preferably includes aprovision, such as a loadlock, to move the inoperative parts to anatmospheric environment for repair operation.

The present invention redundantable robot assembly can be used instocker equipment, such as a wafer stocker, a LCD stocker, or a reticlestocker. It can also be used in processing equipment such as deposition,etching, track, lithography exposure, developer, and bake. It can alsobe used in transport workpieces from a loadlock to a buffer, or to aprocess chamber, to a storage chamber, or to a sorter chamber. It canalso be used in Front End loader, to transfer workpieces from FOUPs toloadlocks.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1A shows a top view of an exemplary redundantable robot assemblyaccording to the present invention, comprising two robots positionedside by side.

FIG. 1B shows a side view, respectively, of an exemplary redundantablerobot assembly according to the present invention, comprising two robotspositioned side by side.

FIG. 2A shows a configuration of two robot assemblies according to anembodiment of the present invention, comprising two robots positionedside by side with offset.

FIG. 2B shows a configuration of two robot assemblies according to anembodiment of the present invention, comprising two robots positioned ontop of each other.

FIG. 2C shows a configuration of two robot assemblies according to anembodiment of the present invention, comprising two robots positioned ontop of each other, also inverted with offset.

FIG. 3 shows a configuration of two robot assembly according to anembodiment of the present invention, comprising two robots having 4 armsegments with multiple degrees of freedom.

FIG. 4 shows a configuration of two robot assembly where there is ablind area where a robot cannot reach if no rotational movement ispermitted after radial movement.

FIG. 5 shows a configuration of two robot assembly where the blind areais eliminated if rotational movement is permitted after radial movement.

FIG. 6 shows a configuration of two robot assembly in application to aconcentric array of workpiece stations.

FIG. 7 shows a configuration of two robot assembly in application tolinear arrays of workpiece stations.

FIG. 8 shows an exemplary configuration where two robots of theredundantable robot assembly of the present invention are located facinga carousel stocker storage area.

FIG. 9 shows an exemplary configuration where two robots of theredundantable robot assembly of the present invention are positioned ona linear track of front end assembly.

FIGS. 10A and 10B show configurations where the robots can be movedlinearly for servicing. FIG. 10A shows an operating configuration, andFIG. 10B shows a configuration where the right robot is moved forservicing.

FIGS. 11A and 11B show configurations where the robots can be movedrotationally for servicing. FIG. 11A shows an operating configuration,and FIG. 11B shows a configuration where the right robot is moved forservicing.

FIGS. 12A and 12B show a configuration for a stocker according to anembodiment of the present invention.

FIG. 13 shows an exemplary computer system for the present invention.

FIG. 14 shows an exemplary computer environment for the presentinvention.

DETAIL DESCRIPTIONS

The present invention relates to an apparatus and method for improvingreliability with moving equipment. The present invention involves aredundancy of the failure-prone parts, e.g. transferred robots, in anequipment to ensure continuous flow of workpieces for a fabricationfacility. An exemplary redundancy of the robot assembly in an equipmentcomprises the duplicate of the robots, plus the redundancy abilitiessuch as the ability to operate one robot when the other is broken, theability of in-situ servicing the broken robot, the ability to calibratethe repaired robot, and the ability to return the repaired robot backinto operation. Operation of the robot assembly includes tolerance onthe position of the robot arms, to prevent hitting the other parts ofthe assembly, especially when the other parts are not operative, andthus cannot move out of the way.

During the processing of semiconductor workpieces in the manufacture ofmicroelectronics, different equipments are employed for several hundredprocessing steps. The process flow of a workpiece is essential serial,with most of the tools operate on the workpieces one at a time. Thefailure of any link in the fabrication process would severely disruptthe process flow, resulting in loss of manufacturing productivity. Thepresent invention provides the handling or movement of workpieces in amanner which assured a continuous flow of workpieces within an equipmentand within a fabrication facility, even in the event of part failures.The present invention discloses a redundancy mechanism for preventequipment failure from affecting the process flow, by allowing theequipment to be functioned, and by allowing the in-situ servicing of thefailure parts.

The present invention thus provides, in an exemplary embodiment,multiple transport mechanisms, such as a plurality of robots, to performessentially the same operations of moving workpieces. A station, such asa wafer or reticle stocker station, is centrally served by a pair ofrobots or workpiece transport mechanisms. Each transport is capable ofaxial motion along a member and pivotal or articulated motion of an arm.The axial motion is used to move workpieces between the stations and thecarrier residing in a load lock, and the articulated arm is used formore constrained motions within the stations, such as swinging betweenstations.

FIG. 1A and FIG. 1B show a top view and a side view, respectively, of anexemplary redundantable robot assembly according to the presentinvention. The robot assembly comprises two independent robots, locatedside by side. The robots as shown comprise a plurality of articulatejoint arms, with a single blade end effector at the end. In otherembodiment, an exemplary robot can include the linear r movement, e.g.extending and retracting, to receive a workpiece, the rotation thetamovement of the articulate arm, and the vertical z movement of raisingor lowering the workpieces. The robots can include several differentmechanisms to perform the movement of the workpieces, such as lineartrack, multi-segmented articulated arms, frog arms, swivel arms,scissors and telescopic mechanism, four-bar linkage mechanism. The robotarm can comprise an end effector to receive a workpiece, such as usinggravitation force, or edge grip force. The end effector might be singleblade of double blade. The robot's movements, such as a combination oflinear and rotational motions, are typically designed to avoid highaccelerations.

The transport mechanism includes a plurality of hands which are drivenindependently of each other. Thus the robot arm has high degree offreedom in movement, and can be able to reach many places. The robot canhave double end effector. The arms of the transport mechanisms may eachhave a fork-like tip. The operations of the redundantable robot assemblyare controlled by a computer system.

A robot arm having the ability to handle two workpieces at the same timecan be used to increase the efficiency of robot handling. The robot canhave two carrier arms located at opposed ends of a support, whichrotates about a pivot. Another robot configuration includes a centralhub having two opposed arms, with a blade linked to the free ends of thearms. A second pair of arms can extend opposed from the first pair, andthus the opposed rotation of the arms in one direction extends the firstarm while retracting the second arm. The arm can use two blades toincreases throughput. Another robot configuration includes a multiplerobot assembly including co-axial upper and lower robot assemblies,which operate independently of each other. The upper robot is typicallystacked above the lower robot and the two robots may be mountedconcentrically. The robot assembly can be constructed with motors suchas servo motors with a synchronous device.

FIGS. 2A-2C show various configurations of two robot assembly accordingto embodiments of the present invention. The two robots can bepositioned side by side with offset, as shown in FIG. 2A. The two robotscan be positioned on top of each other, as shown in FIG. 2B, or invertedwith offset as shown in FIG. 2C. The particular positions of the robotsdepend on the system requirements.

FIG. 3 shows an exemplary configuration for two robots with 4 armsegments and multiple degrees of freedom at each joint. The robot armcan move virtually in all directions with no constraints of r, theta andz as in linear arms.

FIG. 4 shows an exemplary configuration of redundantable robot assemblywith the robot having 3 articulate joint arms. If rotational can onlyperformed before radial movement, the arm of one robot might have ablind area (cross hatched area) where the left robot cannot reach. Ifrotational movement is allowed after radial movement, it can reach theblind area as shown in FIG. 5. The robot can have only one motor controlfor the first arm, with the second arm depending on the movement of thefirst arm. The robot can also have two motor controls, one for rotatingthe first arm, and one for rotating the second arm. The second arm inthis case can move independent of the first am.

FIGS. 6 and 7 show exemplary configurations of redundantable robotassembly for transferring workpieces. FIG. 6 shows a configuration withthe stations located concentric around the robot assembly, and FIG. 7shows a configuration with the stations located in linear arrays aroundthe robot assembly.

The present invention redundantable robot assembly can be used in astocker. An embodiment of the invention comprises a stocker storagearea, comprising workpieces arranged in an array. Two redundant transferrobots are installed at a front side of the stocker array for transferthe workpieces in and out of the stocker. The stocker station caninterface with the tracks in the interbay multilevel track system.Another robot assembly moves the carriers between the stocker andinterbay track system. When the transfer or handling capability isinsufficient with only the first transfer robot, the storage of the lotsin the stocker can be performed by using the second transfer robot aswell. Thus the redundantable robot assembly can improve the throughputof the equipment. The capacity of the stocker can also be designed withthe capacity of the two robots. Since a plurality of transportmechanisms are used, the substrates are transported efficiently, therebyimproving the overall through put of the apparatus as a whole. FIG. 8shows an exemplary configuration where two robots of the redundantablerobot assembly of the present invention are located facing a carouselstocker storage area.

The robot assembly can be used, in one embodiment, in the front endassembly to transfer workpieces between cassettes in a pod assembly. Thefront end assembly generally contains a horizontal motion robot assemblyto move a workpiece to the front end module or to the central module.FIG. 9 shows an exemplary configuration where two robots of theredundantable robot assembly of the present invention are positioned ona linear track, traveling back and forth to transfer workpieces from thefront end assembly to the loadlock of the equipment.

FIGS. 10A and 10B show configurations where the robots can be moved forservicing. FIG. 10A shows a configuration where the two robots are inoperation mode. The robots are connected to a linear guide, where therobots can slide through the guide. FIG. 10B shows a configuration wherethe robot on the right is inoperative, and has been moved to a servicingstation. The left robot can be still operating, and thus, moving theinoperative robot out of the way help prevent disrupting the movement ofthe working robot, together with providing room for servicing theinoperative robot.

FIGS. 11A and 11B show another configuration for servicing theredundantable robot assembly. The moving section comprises a hinge door,where an inoperative robot can be moved out. FIG. 11A shows a workingconfiguration, and FIG. 11B shows that the right robot has been movedout for servicing. Other configurations for servicing also are possible.

FIGS. 12A and 12B show a configuration for a stocker system. FIG. 12Ashows a cross section, and FIG. 12B shows a top view of an exemplarystocker, employing a redundantable robot assembly with two robots.

The robot assembly further comprises a plurality of sensors, such asworkpiece positioning sensors, image sensing of position errors, RFelectric field sensing, magnetic resonance sensing, laser scanning,sensing with photo detector arrays, motor operation sensing, armposition sensing, or any sensors related to the operation and service.Furthermore, the sensors provides the status and locations of the robotassembly, thus allowing the optimum utilization of the remainingoperative part of the assembly, plus the alerting the operator forservicing the inoperative parts of the assembly.

The present invention may also be embodied in a machine or computerreadable format, e.g., an appropriately programmed computer, a softwareprogram written in any of a variety of programming languages. Thesoftware program would be written to carry out various functionaloperations of the present invention. Moreover, a machine or computerreadable format of the present invention may be embodied in a variety ofprogram storage devices, such as a diskette, a hard disk, a CD, a DVD, anonvolatile electronic memory, or the like. The software program may berun on a variety of devices, e.g. a processor.

With reference to FIG. 13, an exemplary environment 300 for implementingvarious aspects of the invention includes a computer 301, comprising aprocessing unit 331, a system memory 332, and a system bus 330. Theprocessing unit 331 can be any of various available processors, such assingle microprocessor, dual microprocessors or other multiprocessorarchitectures. The system bus 330 can be any type of bus structures orarchitectures, such as 12-bit bus, Industrial Standard Architecture(ISA), Micro-Channel Architecture (MSA), Extended ISA (EISA),Intelligent Drive Electronics (IDE), VESA Local Bus (VLB), PeripheralComponent Interconnect (PCI), Universal Serial Bus (USB), AdvancedGraphics Port (AGP), Personal Computer Memory Card InternationalAssociation bus (PCMCIA), or Small Computer Systems Interface (SCST).

The system memory 332 can include volatile memory 333 and nonvolatilememory 334. Nonvolatile memory 334 can include read only memory (ROM),programmable ROM (PROM), electrically programmable ROM (EPROM),electrically erasable ROM (EEPROM), or flash memory. Volatile memory333, can include random access memory (RAM), synchronous RAM (SRAM),dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM(DDR SDRAM), enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM), or directRambus RAM (DRRAM).

Computer 301 also includes storage media 336, such asremovable/nonremovable, volatile/nonvolatile disk storage, magnetic diskdrive, floppy disk drive, tape drive, Jaz drive, Zip drive, LS-100drive, flash memory card, memory stick, optical disk drive such as acompact disk ROM device (CD-ROM), CD recordable drive (CD-R Drive), CDrewritable drive (CD-RW Drive) or a digital versatile disk ROM drive(DVD-ROM). A removable or non-removable interface 335 can be used tofacilitate connection.

The computer system 301 further can include software to operate inenvironment 300, such as an operating system 311, system applications312, program modules 313 and program data 314, which are stored eitherin system memory 332 or on disk storage 336. Various operating systemsor combinations of operating systems can be used.

Input devices 322 can be used to enter commands or data, and can includea pointing device such as a mouse, trackball, stylus, touch pad,keyboard, microphone, joystick, game pad, satellite dish, scanner, TVtuner card, sound card, digital camera, digital video camera, webcamera, and the like, connected through interface ports 338. Interfaceports 338 can include a serial port, a parallel port, a game port, auniversal serial bus (USB), and a 1394 bus. The interface ports 338 canalso accommodate output devices 321. For example, a USB port may be usedto provide input to computer 301 and to output information from computer301 to an output device 321. Output adapter 339, such as video or soundcards, is provided to connect to some output devices such as monitors,speakers, and printers.

Computer 301 can operate in a networked environment with remotecomputers 324. The remote computers 324, shown with a memory storagedevice 325, can be a personal computer, a server, a router, a networkPC, a workstation, a microprocessor based appliance, a peer device orother common network node and the like, and typically includes many orall of the elements described relative to computer 301. Remote computers324 can be connected to computer 301 through a network interface 323 andcommunication connection 337. Network interface 323 can be communicationnetworks such as local-area networks (LAN) and wide area networks (WAN).LAN technologies include Fiber Distributed Data Interface (FDDI), CopperDistributed Data Interface (CDDI), Ethernet/IEEE 1202.3, Token Ring/IEEE1202.5 and the like. WAN technologies include, but are not limited to,point-to-point links, circuit switching networks like IntegratedServices Digital Networks (ISDN) and variations thereon, packetswitching networks, and Digital Subscriber Lines (DSL).

FIG. 14 is a schematic block diagram of a sample computing environment40 with which the present invention can interact. The system 440includes a plurality of client systems 441. The system 440 also includesa plurality of servers 443. The servers 443 can be used to employ thepresent invention. The system 440 includes a communication network 445to facilitate communications between the clients 441 and the servers443. Client data storage 442, connected to client system 441, can storeinformation locally. Similarly, the server 443 can include server datastorages 444.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

1. A redundantable workpiece transfer mechanism for semiconductorworkpiece transfer, comprising at least two independent workpiecetransfer assemblies, wherein each independent workpiece transferassembly is capable of transfer the workpieces regardless of theoperating status of other workpiece transfer assemblies.
 2. A workpiecetransfer mechanism as in claim 1 further comprising providing a servicezone around the workpiece transfer assembly for safe servicing aninoperative workpiece transfer assembly while other workpiece transferassemblies still operating
 3. A workpiece transfer mechanism as in claim1 further comprising an ejection mechanism to move the transfer assemblyto a serviceable area.
 4. A workpiece transfer mechanism as in claim 1further comprising a controller for coordinating the transferring of theworkpieces between the independent workpiece transfer assemblies,wherein the controller recognizes the operating status of the workpiecetransfer assemblies and wherein the controller assigns the transferringof the workpieces to the operating workpiece transfer assemblies.
 5. Asemiconductor equipment having workpiece movement, comprising twostations; a redundantable workpiece transfer mechanism comprising atleast two independent workpiece transfer assemblies for transferring theworkpieces between the stations, wherein each independent workpiecetransfer assembly is capable of transfer the workpieces regardless ofthe operating status of other workpiece transfer assemblies; and acontroller for providing a service zone around the workpiece transferassembly for safe servicing an inoperative workpiece transfer assemblywhile other workpiece transfer assemblies still operating.
 6. Asemiconductor equipment as in claim 5 wherein providing a service zonearound the workpiece transfer comprises restricting the movements ofother worpiece transfer assemblies surrounding the workpiece transferassembly.
 7. A semiconductor equipment as in claim 5 wherein providing aservice zone around the workpiece transfer comprises moving theworkpiece transfer assembly outside the movement ranges of otherworpiece transfer assemblies.
 8. A semiconductor equipment as in claim 5wherein providing a service zone around the workpiece transfer comprisesan ejection mechanism to move the transfer assembly to a serviceablearea.
 9. A semiconductor equipment as in claim 8 wherein the ejectionmechanism comprises a sliding mechanism to slide the transfer assemblyto a serviceable area.
 10. A semiconductor equipment as in claim 8wherein the ejection mechanism comprises a swinging mechanism to swingthe transfer assembly to a serviceable area.
 11. A semiconductorequipment as in claim 5 wherein the transfer assemblies have asubstantially overlapping capability of transferring the workpieces. 12.A semiconductor equipment as in claim 5 further comprising sensors todetect the inoperative state of the workpiece transfer assemblies.
 13. Asemiconductor equipment having workpiece movement, comprising twostations; a redundantable workpiece transfer mechanism comprising atleast two independent workpiece transfer assemblies for transferring theworkpieces between the stations, wherein each independent workpiecetransfer assembly is capable of transfer the workpieces regardless ofthe operating status of other workpiece transfer assemblies; and acontroller for coordinating the transferring of the workpieces, whereinthe controller recognizes the operating status of the workpiece transferassemblies, and wherein the controller assigns the transferring of theworkpieces to the operating workpiece transfer assemblies.
 14. Asemiconductor equipment as in claim 13 wherein the coordinatingcontroller assigns the workpieces to be transferred by an inoperativeworrkpiece transfer assembly to the remaining operating worrkpiecetransfer assemblies.
 15. A semiconductor equipment as in claim 13wherein the controller bypasses an inoperative transfer assembly.
 16. Asemiconductor equipment as in claim 13 further comprising in-situservicing mechanism to allow servicing inoperative workpiece transferassembly while other operative workpiece transfer assemblies are inoperation.
 17. A semiconductor equipment as in claim 13 furthercomprising providing a service zone around the workpiece transferassembly for safe servicing an inoperative workpiece transfer assemblywhile other workpiece transfer assemblies still operating
 18. Asemiconductor equipment as in claim 13 further comprising an ejectionmechanism to move the transfer assembly to a serviceable area.
 19. Asemiconductor equipment as in claim 13 wherein the transfer assemblieshave the same capability of transferring the workpieces.
 20. Asemiconductor equipment as in claim 13 wherein the transfer assemblieshave a substantially overlapping capability of transferring theworkpieces.